The Radial Deformation of Rock Specimen in the Post-faolure Region under the Triaxial Comperession Test.

The triaxial compression test was conducted for Akiyoshi marble, Shirahama sandstone and Berea sandstone with the three kinds of confining pressure, 15 MPa, 25 MPa and 35 MPa. During the test, the radial displacement of the rock specimen was measured by the twelve displacement meters of cantilever type set around the cylindrical rock specimen in every 30° at the center cross section. In order to understand the behavior of the radial deformation with increasing the axial strain in the post-failure region, the measured radial deformation was analyzed by decomposing it into four modes of the deformation. They were isotropic deformation, anisotropic deformation, parallel movement of the specimen and sliding along the generated fault plane. Consequently, for the different rock types and for the different confining pressures, it was cleared that the major deformation mode changed from isotropic deformation to sliding along the generated fault plane, and the point when the faulting is initiated was also cleared. Furthermore, it was cleared that the relationship between the maximum radial strain and the axial strain is almost linear in the post-failure region.